I'm writing up a CV (my secret identity is a mild-mannered software engineer); there's a volunteer project I did (related to my undergrad studies) that I want to describe, and I'm not sure where to put it.

It's a standalone program which completes a certain task. Is that "work experience" because it's basically similar to working? Possibly "Education" because the work was in the context of my degree? Or something else?

And, seeing as this was a side-project which I worked on for a long period but at low intensity - how should I be describing the timeframe of this project?